You may be intimidated the first time you crack open a fake book. However, if you're familiar with (or at least willing to learn) your chords, then that's half the battle.
A fake book contains pieces written out in lead sheet form. That is, you see the melody and chord symbols written above:

The idea is that you "fake" - or create - your own accompaniment. Throw down a pop groove on "Happy Birthday" one day. The next day, you could play it in ragtime style.The possibilities are endless.

Plus, with the music condensed in this format, you can have hundreds of songs in one book. It's so much easier to bring one fake book to a gig than 10 music books.